I did not realize the dealer would paint the body kit. When was that released? I still think it is too much to pay, but if it was painted the same color of the car it would be easier to justify it.

It is not official from GM but pretty much any dealership will do it to make you happy. Most have in house body shops, if not they will have a local shop they work with. Prices will vary from dealer to dealer, maybe even from salesman to salesman, depending on how hard they push to get you a deal. They should be able to do it cheaper than if you were to take it to a shop yourself.

Cost depends on a number of factors. There are different labor rates as well as material rate from city to city, state to state etc. however Bodyshop rates are way lower than the mechanical rates anywhere you go .... even the dealer.
The kit is paintable you need to remove the rear exhaust trim , install the rear defussor lower brackets if not already done so. and hole saw the lower holes in the airdam before paint. We just completed a yellow set for a customer and they came our really nice and the color actually hit dead on. As far as cost you should be able to have them painted for around $ 600.00 no more than 7 .
We also installed the ss stripes on the Hood (pain) and decklid. All this really made the car take on a really sweet look. You may also note is call for you to cut the tips off the exhaust and hammer on some small round tips but we opted to leave the factory ss tips on the car as the customer was looking to replace all the exhaust and wanted to keep the original intact.
another note the painter needs to be aware how this stuff mounts so all the leading visible edges especially the top are covered completely. Did i mention the hood stripes were a pain LOL